Polycystic kidney disease (PKD) is a disease in which the formation of many cysts in the kidney causes an increase of kidney volume and a reduction of renal function and ultimately causes renal failure requiring dialysis. PKD is frequently an inherited disease and can be classified into autosomal dominant PKD (ADPKD) and autosomal recessive PKD (ARPKD). ARPKD is very rare. The ADPKD 1 incidence rate is said to be one per 300 to 500 persons (Non-patent Literature (NPL) 1). A report also says that the number of ADPKD patients treated in medical institutions is only 1 out of 2,000 to 4,000 persons (Non-patent Literature (NPL) 2 and NPL 3). Many patients do not recognize for their entire life that they themselves suffer from ADPKD and thus do not receive appropriate medical treatment (Non-patent Literature (NPL) 3). Therefore, the spread of a more appropriate diagnosis has been desired.
Two kinds of genes, the PKD1 gene (Non-patent Literature (NPL) 4) and the PKD2 gene (Non-patent Literature (NPL) 5), have been identified as ADPKD-causing genes. It has been reported that the patients resulting from a mutation in the PKD1 gene account for 85% to 90%, whereas the patients resulting from a mutation in the PKD2 gene account for 10% to 15% (Non-patent Literature (NPL) 6). When patients have an abnormality in the PKD1 gene, the average age of shifting to dialysis is 53. Compared with 63, which is the age at which patients with an abnormality in the PKD2 gene shift to dialysis, the progression of the disease in patients having an abnormality in the PKD1 gene is fast (Non-patent Literature (NPL) 7). There are various types and positions of disease-causing mutations in PKD1 and PKD2 genes. Disease-causing mutations characteristic of particular pedigrees exist (Non-patent Literature (NPL) 8).
At present, for definitive diagnosis of ADPKD, diagnostic imaging using CT, MRI, and ultrasonic tomograms is performed and diagnosis is made based on the number of cysts that can be confirmed in the kidneys. However, this diagnostic method cannot be used until cysts are formed. Therefore, it is impossible to know whether the patient is a PKD gene mutation carrier before the formation of many cysts. If technical innovations provide an environment in which PKD gene diagnosis can be more easily utilized, it is expected to assist definitive diagnosis of PKD mutation carriers who have not yet developed the disease and also become possible to grasp the difference in disease progression rate by identifying the gene and region in which a mutation exists.
As methods for detecting mutations in PKD1 and PKD2 genes, (1) mutation detection using the Sanger method (Non-patent Literature (NPL) 9), (2) mutation detection using DHPLC (denaturing high-pressure chromatography) (Non-patent Literature (NPL) 10), (3) mutation detection using endonuclease and DHPLC (Non-patent Literature (NPL) 11), (4) mutation detection using a next-generation sequencer (Non-patent Literature (NPL) 12), and like methods have been reported.